Charge for solid propellent rocket



Aug. 24, 1965 R. v. BANCELIN CHARGE FOR SOLID PROPELLENT ROCKET Filed Nov. 17. 1961 United States Patent Oiice blii Patented Aug. 24, 1965 3,201,936 vCI-liA'RGE FR SOLID PROPELLENT ROCKET Robert Victor Bancelin, 45 RuerProu,

Ciaye-sous-llois, France Filed Nov; 17, 1961, Ser. No. 153,086 Claims priority, applicsation France, Nov. 29, 1960,

7 claims. (5cl. s0-,356)

This invention relates to propulsion units for .rockets driven by reaction, and theV object of the invention is more particularly to improve the combustion of the solid charges used for propulsion, more especially to increase the duration of combustion of a given charge and to render the said combustion uniform.

It has already been proposed to provide in apropulsion unit a solid fuel charge in the form of a cylinder, and to effect the combustion of this charge from its face adjoining the reaction nozzle (cigarette combustion). The combustion, which in this case is effected in a plane strictly limited'toV the cross-section of the chamber, progresses axially away fronrthe discharge nozzle, with the disadvantage of being accompanied by a displacement of the centre of gravity of the propulsion unit; this makes it necessary to provide delicate and expensive correcting devices for the rocket.

, According to a further prior proposal, the cylindrical charge block which is provided with a central` duct has a Vcross-section which is either circular or star-shaped or else the block is in the form of a rectangular paratilelepiped having a cross-shaped cross-section. In this case combustion is effected over the entire length of the block, in the direction from the interior towards the .exterior in the case of the cylindrical block of circular or star-shaped cross-section, and conversely in the case of the cross-shaped parallelepipedic block. I y

This kind of combustion is more uniform thanthat previously described, and does not cause a modication of the position of the centre of gravity, but the duration of combustion is still rather short. Furthermore, this kind of combustible block being generally constituted by a crushed material agglomerated in a suitable manner, there is`risk that it may have defects, porosity, shrinkage cavities, poorlyvgelatinised parts, which hinder the progressive combustion and can even go so far as to cause the rocket to burst.

In order togincrease the duration of combustion, the invention proposes a charge for rockets which is char, acterised in that it comprises means for ensuring combustion in at least one plane passing through the axis of the rocket and rotating about the said axis, or in only one or more parts of an axial plane.

In such a propulsion unit, the surface in a stateV of ignition is considerable, and its rotation about the axis makes it possible to obtain a long duration of combustion, Furthermore, since at each instant the burning surface implicates an axial surface, it permits a small maxi-Y mum cross-section for 'the rocket, whilst providing strong thrust.

The progressof the burning face about the axis of the rocket can be nonuniform at diierent points along a radius of the charge. Unless any specialrmeasures wereV taken, the portion of the charge near to the axis would burn away more quickly than the portion of the charge neaiythe periphery. In order. to regularise this combustion, the invention also proposes constructing the being suitably chosen for ensuring uniform combustion in successive radial planes.

This uniform combustion can also be obtained by varying other factors than the size of the grains, for example by constituting the charge of powders which burn more or less quickly with relation to one another, or by providing in the mass of the charge combustion-retarding or combustion-accelerating agents, or by using two or more of these measures simultaneously.

According to a first form of embodiment of the invention, with the aim of eifecting the kind of combustion already indicated, the charge comprises in its hollow axial portion a shield which is for example cylindrical and has a lateral aperture one lip of which is prolonged by a wall extending to the periphery of the charge.

According to a varient, the charge is divided in the sense of its height into two or more sections separated from one another by sheet metal plates covered with a refractory material, each section of the charge comprising in its hollow axial portion a shield whichris, for example, cylindrical and has a lateral aperture one lip of which is prolonged by a wall extending to the periphery of the corresponding section and the walls of the successive sections being oiset relatively to one another by an appropriate angle in order to avoid the unbalance occurring during combustion.

Thus, if the charge is subdivided into two superposed sections, this amount of oifset will be 180 if there are three sections, the offset will be 120; in the case of four sections, it will be 90, and so on.

According to a further form of embodiment, the axial hollow in the charge is lined with two screens which are for example cylindrical and are noncontiguou's, the opposite Vertical faces of these two screens each being prolonged by a wall extending to the periphery of the charge. Finally, according to a variant, the wall extending to the periphery of the charge is in the form of a constantpitch or variable-pitch helical surface whose pitch is preferably but not necessarily equal to the height of the said charge.

The invention also covers a variant wherein the hollow axial portion protected by a screen is iilled with a slug of powder of conventional form (having a circular, starshaped or cross-shaped cross-section) which is ignited at the time of takeoff, thus guaranteeing more perfect ignition of the propulsion unit which is the subject of the invention, and if this slug is made with a suitable powder it is possible to provide the rocket with a considerable supplementary acceleration as it takes oi.

. A charge according to the invention reduces the known disadvantages resulting from the displacement of the centre of gravity during the course of combustion, and

charge with grains of diierent sizes. Thus, the part of i also the other disadvantages referred to hereinbefore in connection with known charges.

By way of example, a description will now be given of various embodiments of the invention illustrated dialgrammatically in the accompanying drawings wherein:

FIGURE 1 is an axial sectional view of a propulsion unit according to the invention.

4 FIGURE 2 is a sectional view on the line II-II of FIGURE 1.

FIGURE 3 is a diagrammatic perspective view of a variant of a charge according to the invention. FIGURE 4 is a view similar to that of FIGURE 2 showing a4 modiied form of embodiment of the charge. A

FIGURE 5 shows in perspective a helical wall which can Vbe used in the charges according to FIGURE 2 or 4.

The propulsion unit of FIGURE 1 comprises a cylindrical casing 1 provided at its ends with screw-threading 2, 3 and closed at the top (in the drawing) by a cover 4 carrying the ignition device 5, and at the bottom by a cover 6 carrying the discharge nozzle 7 in known manner. On the inner face of the cover 6 provided with a central aperture there is arranged a disc S also having a central aperture and a metal tube 9 which is situated axially through the propulsion unit and is lined internally with a refractory material 1i?. In the annular chamber bounded by the casing 1 and the tube there is arranged the charge 11 of the propulsion unit, provided with a lining 12 covering all its faces. The reference numeral 13 designates an elastic device or spring washer which bears against the cover and the charge 11 to maintain the latter against the bottom of the casing.

As FIGURE 2 shows, the metallic tube 9 and its linings and 11 is split along a generatrix to provide a slot 15 and to one of the lips of this slot there is connected a radial metallic shield 16 comprising on its faces the same linings as the tube. Directly in line with the slot 15 the combustible block of the propulsion unit is formed with a radial channel 17.

By means of this arrangement, the gases for the reaction propulsion of the rocket are those coming from the combustion of the face 18 which is the only burning face and which is displaced in the directions of the arrows 19, turning about the axis of the propulsion unit. The duration of combustion of the charge which has just been described is much longer than that of an identical charge which is burned by the known combustion methods referred to earlier hereinbefore.

In order that the burning surface is propagated along radial planes, the charge, which is a block of solid propergol, is to be of varying combustion rates in accordance with radial direction, the slow-combustion powders being situated in the zone adjoining the axis of the powder slug, the rapid-combustion powders being situated towards the periphery.

In some cases, it will be advantageous to provide in the central channel 10 a slug of powder of conventional form, for example a slug constituted by a cylindrical block having an axial discharge duct therein,and star-shaped, for example in cross-section. At the time of take-off, it is the slug introduced into the central channel 10 which is ignited by the ignition device 5 and which at the end of its combustion ignites the face 18 of the main charge. This makes it possible to perfect the reliable ignition of the charge 11 and to obtain a strong supplementary acceleration at the take-off of the rocket if the slug is constructed with a suitable powder.

In the embodiment shown in FIGURES 1 and 2, the combustion of the charge is effected in successive radial planes, being propagated in the direction of the arrows 19 from the radial face 18. This progressive travel of the burning face introduces a certain unbalance which may be troublesome in some cases.

In order to remedy this, resort may be had to the embodiment illustrated di-agrammatically in FIGURE 3. According to this embodiment, the charge is subdivided into two sections 11' Iand 111", separated `by a sheet metal plate 8 covered with a refractory material (not shown), each section 11', 11 being constructed in accordance with FIGURE 2 with channels 17', 17, shields and radial Walls (not shown) extending to the periphery, and the two sections bein-g offset radially by 180 so that the burning faces 18 and 18 are situated substantially in one and the same plane and the ignition is propagated in the direction of the arrows 19 and 19". It will be noted immediately that this kind of charge whose duration of combustion is equal to that of the charge in FIGURES 1 and 2 (if the charge 11 and th-at constituted by the sections 11 and 11" .are constructed with the same powder and to the same dimensions) burns without any unbalance.

It is, of course, lpossible to multiply the number of sections to be assembled as shown in FIGURE 3, and in the case of a number of sections greater than 2, it is suit- .able to offset them angularly relatively to one another so as to obtain a combustion which does not introduce any unbal-ance. Thus, in the case of three sections, these are offset by 120 from one another, and in the case of four sections the .angle of offset will be etc. Care will be taken to place between two successive sections a sheet metal disc covered wit-h a refractory material, or, more generally, -a means capable of preventing the burning face of one section from igniting the adjoining section. An advantageous method of constituting a charge according to FIGURE 3 is to construct a block having substantially the height of the propulsion unit, to cut it into'as many sections as is desired and then to superpose these sections with the desired amount of offset relatively to one another in the propulsion unit, taking care to separate the successive sections as indicated.

The construction of the charge shown in FIGURE 4 is similar to that of FIGURE 2 in that it also comprises means for ensuring combustion along a Iburning face which rotates -about the axis, but according to FIGURE 4 these means are such that there are two burning faces 20, .21 progressing in the direction of the .arrows 22, 23 by rotation about the axis of the char-ge and affecting the entire height of the charge. For this purpose, the axial outlet duct is formed by two sheet metal elements 9, 9', for example semi-cylindrical in form and non-contiguous so Ias to leave two slots `15, 1S', the two sheet metal elements being prolonged respectively by shields 16, 15' at the two opposite ends of the said elements.

The slot or slots 15 or 15 and 15 do not need to be parallel to the axis of the charge. They can be helical and according to one advantageous form of embodiment, the `pitch of the helix thus formed is equal to the height of the charge, as illustrated in FIGURE 5, wherein the opposite shields 24 Iand 25 are also helical. In this ernbodiment, the assembly of the walls shown in FIGURE 4 is buried in the mass of the charge whose combustion is also effected Iby the burning of the two radial faces rotating about the axis of the charge, measures being taken, .as in the previous case, to ensure that combustion is al- Ways effected in an axial plane of the charge.

Other variants can be envisaged within the framework of this invention. Thus, the discharge duct provided by means of the walls 9 Iand 9 may be made of .a material other than sheet metal, the said duct may be conical in form and in this case it is preferable for the charge to be of the same shape; it can -be split longitudinally and associated wit-h a helical shield.

The invention is, of course equally applicable to cornposite powder-liquid propulsion units and to devices having a plurality of propulsion units placed in a star-shaped formation about the axis of the assembly.

What'I `claim is:

1. In a rocket propulsion unit a noncombustible casing having a longitudinal axis of revolution, a combustible .charge contained in said casing and having a coaxial perforation, a noncombustible tube coaxially located in said perforation and having a lateral aperture, and at least a noncombustible wall radially extending to the periphery of said charge and connected to said internal tube along one edge -of said later-al aperture.

2. A rocket propulsion unit according to claim 1, in which the speed of combustion of the charge increases from the axis of revolution towards the periphery.

3. VIn a rocket propulsion unit having a longitudinal axis of revolution, a coaxial combustible charge having la coaxial perforation, said combustible charge being divided along the longitudinal axis into at least two sections, noncombustible plates separating said sections, a noncombustible wall radially extending to the periphery of the .charge in each section, said walls being offset angularly to one another in the `adjacent sections of the charge.

4. In .a rocket propulsion unit a noncombustible casing having a longitudinal axis of revolution, a combustible charge contained in said casing and having a coaxial perforation, a noncombustible tube coaxially located in said perforation .and having at least a lateral aperture, at least a radial slit from said axial perforation to the periphery of 4said charge, a noneonibustlible Wall protecting only lone yside of said radial slit, and .tixedly connected to said tube .along one edge of said lateral aperture.

5. In a rocket propulsion unit laccording to claim 4 the noncombustible tube comprises two diametrally opposed lateral apertures, two radial slits extending in prolongation of one .another to` the periphery of the charge and two noncombustible Wal-ls situated in the same plane and protecting only one side of each radial slit.

6. In a rocket propulsion unit according to claim 1, the wall extending from the noncombustible tube to the periphery of .the ycharge is in the `forrn of `an helix coaxial with the charge and whose pitch is equal to the longitudinal dimension of the charge.

7. In a rocket propulsion unit having 'a longitudinal -axis of revolution, a combustible charge having a hollow longitudinal axial portion, .a shield located in said hollow longitudinal portion and having la later-a1 aperture, and a wall extending to the periphery of the charge and xedly connected to said shield .along one edge of said 20 lateral aperture, said shield and .said Wall being made of a noncom-bustible material coated with a refactory material.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Jet Propulsion, publication, vol. 26, No. 2; February 15 1956 (pp. 102 and 103).

MARK NEWMAN, Primary Examiner.

SAMUEL LEVINE, CARLTON R. CROYLE,

Examiners. 

1. IN A ROCKET PROPULSION UNIT A NONCOMBUSTIBLE CASING HAVING A LONGITUDINAL AXIS OF REVOLUTION, A COMBUSTIBLE CHARGE CONTAINED INSAID CASING AND HAVING A COAXIAL PERFORMATION, A NONCOMBUSTIBLE TUBE COAXIALLY LOCATED IN SAID PERFORATION AND HAVING A LATERAL APERTURE, AND AT LEAST A NONCOMBUSTIBLE WALL RADIALLY EXTENDING TO THE PERIPHERY OF SAID CHARGE AND CONNECTED TO SAID INTERNAL TUBE ALONG ONE EDGE OF SAID LATERAL APERTURE. 